In the resource recovery industry, resources (such as hydrocarbons, steam, minerals, water, metals, etc.) are often recovered from boreholes in formations containing the targeted resource.
Generally, when running a tubing string downhole, it is desirable, and in some cases required, to include a safety valve on the tubing string. The safety valve typically has a fail-safe design whereby the valve will automatically close to prevent production fluid from flowing through the tubing, should, for example, the surface production equipment be damaged or malfunction.
Should the safety valve become inoperable, the safety valve may be retrieved to surface. The tubing retrievable surface controlled subsurface safety valve (“TRSV”) is attachable to production tubing string and includes a flapper pivotally mountable on the lower end of the safety valve assembly, and biased in the closed position to prevent fluid flow through the tubing string. When fully closed, the flapper seals off the inner diameter of the TRSV preventing fluid flow therethrough. A flow tube is provided above the flapper to open the flapper. The flow tube is adapted to be movable axially within the TRSV. When the flapper is closed, the flow tube is in its uppermost position; when the flow tube is in a lowered position, the lower end of the flow tube operates to extend through the TRSV and pivotally open the flapper. When the flow tube is in the lowered position and the flapper is open, fluid communication through the TRSV is allowed. To move the flow tube to the lowered position, a piston rod is engaged with the flow tube. The piston rod is located in a hydraulic piston chamber within the TRSV. The upper end of the chamber is in fluid communication, via a control line, with a hydraulic fluid source and pump at the surface. Seals are provided such that when sufficient control fluid (e.g. hydraulic fluid) pressure is supplied from surface, the piston rod moves downwardly in the chamber, thus forcing the flow tube downwardly, against the bias of a power spring, towards the flapper to open the TRSV. When the control fluid pressure is removed, the piston rod and flow tube move upwardly by the power spring, allowing the flapper to move to its biased closed position.
Due to the potential for the flow tube to rotate during longitudinal translation through the TRSV, the coupling between the flow tube and the piston rod must allow for flow tube rotation, while ensuring that the piston rod is protected from rotational loads due to its confinement within the piston chamber. The piston rod has been connected to the flow tube with a stop seal which fits under a thrust sleeve and is retained in the thrust sleeve by the outer diameter of the flow tube. However, in extreme cases, the stop seal can ‘pull through’ from the thrust sleeve.
The art would be receptive to alternative and improved valves and methods to manufacture valves in the resource recovery industry.